balancing selection at the tomato rcr3 guardee gene family maintains variation in strength of pathogen defense平衡选择在番茄rcr3卫士基因家族维护病原体防御强度的变化.pdf

Balancing Selection at the Tomato RCR3 Guardee Gene Family Maintains Variation in Strength of Pathogen Defense ¨ 1,2¤ 2 1 ´ 1 Anja C. Horger *, Muhammad Ilyas , Wolfgang Stephan , Aurelien Tellier , Renier A. L. van der Hoorn2 , Laura E. Rose1,3 1 Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Planegg-Martinsried, Germany, 2 Plant Chemetics Lab, Chemical Genomics Centre ¨ of the Max Planck Society, Max Planck Institute for Plant Breeding Research, Cologne, Germany, 3 Institute of Population Genetics, Heinrich Heine University Dusseldorf, ¨ Dusseldorf, Germany Abstract Coevolution between hosts and pathogens is thought to occur between interacting molecules of both species. This results in the maintenance of genetic diversity at pathogen antigens (or so-called effectors) and host resistance genes such as the major histocompatibility complex (MHC) in mammals or resistance (R) genes in plants. In plant–pathogen interactions, the current paradigm posits that a specific defense response is activated upon recognition of pathogen effectors via interaction with their corresponding R proteins. According to the ‘‘Guard-Hypothesis,’’ R proteins (the ‘‘guards’’) can sense modification of target molecules in the host (the ‘‘guardees’’) by pathogen effectors and subsequently trigger the defense response. Multiple studies have reported high genetic diversity at R genes maintained by balancing selection. In contrast, little is known about the evolutionary mechanisms shaping the guardee, which may be subject to contrasting evolutionary forces. Her